A dangerous parasite known as the New World Screwworm (NWS) has been detected just 700 miles from the U.S. border, raising alarms among ranchers, wildlife managers, and federal authorities. The fly, whose larvae infest and feed on the flesh of living animals, poses a serious threat to livestock, wildlife, and local economies if it crosses into the United States.
The screwworm fly lays its eggs in open wounds or the soft tissue of animals. When the eggs hatch, the larvae burrow into flesh, causing intense pain, infection, and often death if left untreated. Outbreaks can spread rapidly through herds, especially in warm climates with large animal populations.
Texas, with its vast cattle operations and thriving hunting industry, is particularly at risk. An outbreak in the state could cost ranchers millions and significantly disrupt rural economies that depend on livestock and wildlife management.
The last major screwworm outbreak in the U.S. occurred in 1982. Since then, federal and regional efforts, including sterile fly release programs and strict animal inspection protocols, have kept the parasite out. However, recent cases in the Caribbean and South America, combined with increased trade and travel, have reignited concerns that the pest could return.
In response to the recent detection of screwworm in regions closer to the U.S. border, federal lawmakers and agricultural agencies are moving quickly. Measures include expanding sterile-fly facilities in the U.S., strengthening inspection of imported animals, and updating emergency response protocols for containment.
“The immediate response will be to lock areas down, create quarantine areas, and stop livestock and people moving around,” said Andrew Coppin, CEO of Ranchbot, an agricultural technology firm that monitors livestock health.
Coppin emphasized the importance of early planning and coordination between landowners, state officials, and federal agencies. Minimizing unnecessary movement of livestock and tracking any symptoms of infestation will be vital to stopping a potential outbreak in its early stages.
If screwworm were to reach U.S. herds, the economic impact could be severe. Texas alone is home to more than 12 million cattle and a large population of white-tailed deer, which are also vulnerable to the parasite. Infected animals require immediate veterinary treatment, and areas with infestations must be quarantined, disrupting both domestic and international trade.
Wildlife experts also warn that a screwworm outbreak could have ecological consequences. Native species, including deer, wild pigs, and small mammals, could act as hosts and contribute to the spread of the parasite. Managing wildlife exposure is especially difficult in rural and border regions where monitoring is limited.
Beyond the biological threat, there are logistical challenges. Border regions often lack the veterinary infrastructure needed for rapid diagnosis and treatment. Remote ranches may not have the resources to implement biosecurity measures without state or federal support.
Coppin believes the success of any response will depend on more than just technology or government action. He points to the need for shared responsibility and proactive decision-making by individual ranchers and landowners.
“Our livestock, our economy, and our way of life depend on staying ahead of these threats with smart systems and proactive policy,” he said.
Officials at the U.S. Department of Agriculture are coordinating with international partners in Mexico and Central America to monitor the parasite’s movement and support regional containment efforts. Some experts argue that long-term investment in cross-border surveillance and education will be necessary to prevent future outbreaks.
Public awareness is also key. Livestock owners are encouraged to inspect their animals regularly, report suspicious wounds or behavior, and follow any local guidance from agricultural authorities. While screwworm is not a direct risk to humans, the larvae can infect pets and other domestic animals if left untreated.
Veterinarians, especially those in southern states, are being advised to remain on alert and review best practices for identification and reporting. The earlier an infestation is caught, the better the chances of avoiding large-scale consequences.
As summer temperatures rise and insect activity increases, officials hope that early action will keep screwworm outside U.S. borders. For now, planning, cooperation, and vigilance remain the best defense against this flesh-eating threat.
